Fuel cells are power generating devices. Specifically, H2—O2 proton exchange membrane fuel cells are fuels cells that use hydrogen gas and oxygen gas as fuel to generate electrical energy through the reaction of the hydrogen and oxygen. Fuel cells generally comprise of a fuel cell stack, sources for the hydrogen and oxygen, humidifying systems, cooling systems, and control systems. FIG. 1 shows an example of a typical H2—O2 fuel cell using existing technology where (21) is the hydrogen source, (22) is the humidifying system for the hydrogen, (23) is the oxygen source, (24) is the humidifying system for the oxygen, (25) is the hydrogen pressure release valve; (26) is the oxygen pressure release valve, (27) is the hydrogen release valve, (28) is the oxygen release valve, (29) is the circulating pump for hydrogen, (30) is the cooling system, (31) is the external load, and (32) is the fuel cell stack. Many existing fuel cells do not include the circulating pump (29). Two types of cooling system, liquid cooling and air cooling, can be used. Air cooling is primarily used in cells generating less than 1000 watts which produce less heat. A small fan is usually sufficient for air cooling. Cells generating over 1000 watts produce more heat and must be liquid cooled to release the heat. This cooling method is relatively complicated because it requires a variety of equipment such as pumps, heat exchangers, and water processing devices.
The fuel cell stack (32) is the key component in the H2—O2 proton exchange membrane fuel cell. It comprises of one or more membrane electrode assemblies and flow field plates. The membrane electrode assemblies are where fuel reactions occur and it comprises of a proton-exchange membranes, catalyst layers on both sides of the membrane, and gas-diffusion layers. Flow field plates are graphite or metal plates with flow channels on their surfaces. If these channels are blocked, then the fuel or fuels cannot reach the surfaces of the catalyst layers and cell reactions that generate electricity cannot occur.
For H2—O2 fuel cells, the reactions in the fuel cells are:                a. anode: H2−2e=2H+        b. cathode: ½O2+2H++2e=H2O        c. Total reaction: H2+½O2═H2O        
The above reaction equations indicate that, for each 1 Ah of electricity, a fuel cell stack with a single cell will generate 0.0187 mol (0.34 g) of exhaust, water, at the cathode. During fuel cell operation, water will gradually accumulate in the flow channels of the flow field plates and block the passage for the fuel to reach the membrane electrodes and react, unless the generated water is discharged from the fuel cell. The water is either vaporized and released with the reacting gases or released in liquid form with the reacting gases.
The theoretical oxygen consumption in H2—O2 fuel cells is 21% of the theoretical air consumption in hydrogen-air fuel cells at the same current. Therefore, under the same power conditions, the amount of exhaust released by H2—O2 fuel cells is far less than that of hydrogen-air fuel cells. Even without humidification, most of the water generated by the H2—O2 fuel cells is generally released in liquid form. The gaseous exhaust of hydrogen-air fuel cells is primarily impurities such as the nitrogen from the air. Pure oxygen gas also contains 0.01˜0.05% of impurities. If the exhaust is not released after a few hours of continual operation, the performance of the fuel cell will be compromised when the density of the impurities of the fuel in the channels becomes too high. In addition, releasing the gaseous exhaust also discharges the liquid water that is generated. In order to easily discharge this water with the release of the gaseous exhaust, the fuels, i.e., the fuels that are reacting, must maintain a fairly high flow rate. However, increasing the flow rate will also result in the release of the large volumes of the unreacted fuel thus reducing the efficiency of the cell.
Existing technology generally increases the flow rate of the fuel such as hydrogen or oxygen by improving the design of the flow field plates and reducing the cross sectional area of the flow channels. This will enhance the ability of the exhaust to discharge the water and reduce the quantity of fuel used or consumed. However, since the theoretical quantity of the consumed oxygen is very small, its ability to discharge water is also limited. Even when the design of the flow field plates is optimized, the actual quantity of consumed oxygen for adequate discharge of water needs to be twice the theoretical quantity.
To improve the utilization rate of the fuels, more advanced fuel cell systems recycle the exhaust back into the reacting gas pipeline with pressurized pumps after passing the exhaust through a gas-water separation apparatus. This can reduce the loss of unreacted fuel during the release of exhaust, and lower the use of the fuel. However, this method can also increase the power consumption of the system and limit the total increase in energy efficiency. In addition, this type of design increases the complexity of the system and therefore, also increases the cost for manufacturing such system.
Due to the limitations of the prior art, it is therefore desirable to have novel fuel cells and novel methods for supplying fuels, releasing gaseous exhaust, and discharging liquid such as water in order to manufacture fuel cells that produce low emissions and are highly energy efficient.